Google Antigravity SDK 0.1.21

Changelog: Experimental API isolation with @beta namespaces, declarative subagent skills configuration, and bulk hook registration

This release introduces experimental API isolation using the @beta decorator and .beta namespaces, granular skills configuration for subagents, and bulk hook registration during agent initialization. It also expands typing support for tool context annotations, refines UsageMetadata arithmetic operations, and resolves an issue where tool calls with empty string IDs were unintentionally deduplicated.

Improvements(9)

• Experimental API isolation with beta namespaces: Introduces the @beta decorator and google.antigravity.beta module, enabling access to preview and experimental features on class and instance namespaces without polluting the stable API surface.
• Declarative subagent skills configuration: Adds skills_config support to SubagentConfig, allowing developers to explicitly configure subagent skill inheritance, override skills, or isolate subagents from parent skills.
• Bulk hook registration: Enables registering sequences of hooks at once during Agent session initialization and within HookRunner.
• Beta API decorator and namespace: Added @beta and BetaNamespace support to expose preview classes, methods, and properties under dedicated .beta accessors and google.antigravity.beta.
• Subagent skills management: Added SubagentSkillsConfig, SubagentInheritSkillsConfig, SubagentNoneSkillsConfig, and SubagentOverrideSkillsConfig to SubagentConfig for declarative control over subagent skills.
• Session hook collections: Updated HookRunner and Agent session initialization to accept collections of hooks in addition to individual registrations.
• Qualified typing in tool annotations: Expanded ToolRunner string annotation inspection to resolve qualified typing wrappers (typing.Optional, typing.Union, and typing.Annotated) when injecting ToolContext.
• UsageMetadata arithmetic: Harmonized UsageMetadata.__sub__ typing and zero-value identity behavior to align with UsageMetadata.__add__.
• Tool inspection: Added __repr__ to ToolWithSchema for clearer terminal output and debugging inspection.

Fixes(1)

• Tool call deduplication: Fixed an issue in Conversation.receive_chunks() where tool calls with empty string IDs (id='') were treated as duplicate IDs and dropped; they are now treated as absent IDs and yielded correctly.

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